1. Field of the Invention
The present invention relates to power supplies and more particularly to power supplies capable of operating while receiving a wide range of input power such as occurs in vehicular battery supplies.
2. Description of the Prior Art
A battery operating in a mobile vehicular application described by MIL-STD-461C for line voltage experiences severe transients during vehicle operation. A conventional Pulse-Width-Modulated (PWM) voltage regulator which controls the output voltage to a defined set point can typically tolerate input variations over a range of input voltages where the maximum to the minimum ratio is about 3.5. This voltage range on the input corresponds to a duty cycle for the PWM regulator from about 15% to 85% which is near the current optimum design parameters for many PWM power supplies.
In prior art power supplies the PWM operation was designed for the operating levels of FIG. 2 describing the high and low transient voltage levels. The design was optimized around the normal steady state (26 VDC) and achieved high efficiency without shutting OFF when operating between the high level (42 VDC) and the low level (12 VDC) transient boundaries of voltage. The power supply operation was disabled outside this locus of operating points, causing a loss of operating power to the system.